Psoriasis, asthma and inflammatory bowel disease (IBD) are characterized by a primary neutrophil and eosinophil infiltration at the inflammatory sites. 5-Oxo-ETE (5-oxo-6E,8Z,11Z,14Z-eicosatetraenoic acid) is a potent activator of both neutrophils and eosinophils and among lipid mediators; it is the most active eosinophil chemoattractant so far tested. This raises the possibility that this compound is an important mediator of inflammation, especially in conditions associated with eosinophilia. The major focus of this application is the development of a variety of tools that will be used to investigate the biosynthesis, metabolism and physiological role of 5-oxo-ETE. A primary goal will be to synthesize affinity ligands and photoaffinity probes, based on 5-HETE, to permit the purification, labeling and ultimate cloning of 5-hydroxyeicosanoid dehydrogenase, the enzyme responsible for the formation of 5-oxo-ETE. Similar approaches will be used to develop affinity ligands related to 5-oxo-ETE. These will be used to characterize metabolic enzymes (5- oxo-eicosanoid-D6-reductase and 5-ketoreductase) as well as the 5-oxo-ETE receptor. We recently found that human platelets convert 5-oxo-ETE to a metabolite (5-oxo-12S-HETE) that antagonizes 5-oxo-ETE-induced calcium mobilization, and we propose to use this as a lead compound to develop more potent antagonists. Another major or goal is to investigate the metabolism of other oxo-eicosanoids, including 12-oxo-LTB4. We found that this compound is converted by keratinocytes in a highly stereospecific manner to a series of cysteinyl-containing metabolites c-LTB3, d-LTB3 and e-LTB3, similar in structure to the potent cysteinyl-leukotrienes LTC4 and LTD4 and we propose to further investigate the mechanism for the formation of these compounds. In addition, we will investigate reductive pathways responsible for the conversion of 12-oxo-ETE to the potent proinflammatory agent 12-HETrE (12R-hydroxy-5Z,8Z,14Z-eicosatrienoic acid).